The effect of chemical etching and nanostructure additive epoxy coating technique on adhesion strength in aluminum joints bonded with nanostructure additive adhesive

In the present study, in order to increase the strength of adhesively bonded joints, the surface of the adherend was chemically etched with an anodizing treatment process at different temperatures and the surface was coated with nanostructure doped epoxy. Additionally, carbon nanostructures were added to the adhesive at different ratios to increase the strength of both the adhesive and the joint. In the study, in order to clean the surfaces of AA2024-T3 aluminum alloy plates and eliminate the oxide layer, the plates were chemically treated with a sodium hydroxide solution. Afterwards, the surfaces of these aluminum alloy plates were chemically etched with an anodizing treatment process at temperatures of 25, 40 and 60 °C. The aim here is to create different surface roughness and surface energy on the aluminum alloy surface. Epoxy pre-coating (EPC) was applied to the chemically etched aluminum alloy surfaces. Furthermore, a single-lap joint was produced by adding 0.5 %, 1 % and 2 % carboxylated carbon nanotube (CNT-COOH) by weight to the EPC and adhesive applied to the surfaces and the failure loads of the joints were examined. As a result, when the failure load obtained from the experiments was examined, it was found that chemical etching alone increased the joint strength by 22 % while the chemical etching and EPC application increased it by 46 %, the chemical etching and nanostructure doped EPC application increased it by 61 % and nanostructure addition to the adhesive increased it by 93 %. However, these increases in joint strength vary depending on the duration of the anodizing treatment process and the nanostructure additive ratio. In the chemical analyses performed to interpret these results, surface roughness test, surface contact angle test, X-ray photoelectron spectroscopy (XPS), fourier-transform-infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and images obtained from the failure surfaces were used, respectively.